Yestonians (Estonian: jeestlased, jeestlane) was the derogatory epithet for Estonians brought from Russia to Estonia after World War II to staff the political structures of the Soviet Estonia with loyal cadre. The term is related to the heavy Russian accent of these people, for many of whom their mother language was second language  Specifically, the correct Estonian words for "Estonians" are eestlased, eestlane, and the term derides the Russian accent for the first vowel of the word Eesti (Estonia) as in the word "yes", rather than similar to the one in "end."
As Mart Laar wrote, in 1946 the Communist Party of Estonia comprised 52% Russians, 27% of local Estonians and 21% of "Yestonians". Moscow distrusted local communists, and by 1952 the upper echelons of CPE had eventually become occupied by Russians and Yestonians. During the Khrushchev Thaw the number of ethnic Estonians in CPE gradually increased, especially in lower echelons, but still in 1966, the CPE Central Committee had only about 27% of local Estonians.
Another demographic distinction between native and "Russian" Estonians was age. In hopes for gaining more autonomy within the Soviet Union, around 1956 many young Estonians joined CPE, while Yestonians were mostly of older generation.
While some of them tried to re-acculturize, such as Ivan Kebin, who renamed himself to Johannes Käbin and notably improved his command of Estonian, most others remained Russian by culture and language.